Objective: To identify the relationship between dysphagia, dietary level, and pulmonary function in post-stroke patients. Methods: Thirty-six post-stroke patients with dysphagia, who were hospitalized from June 2017 to October 2017 in the Department of Rehabilitation Medicine at a tertiary hospital, were analyzed retrospectively. The video-fluoroscopic swallowing study (VFSS) and videofluoroscopic dysphagia scale (VDS) were used to assess dysphagia. The vital capacity (VC) and peak cough flow (PCF) were used to assess the pulmonary function. Upon admission, the patients were divided into three groups according to their dietary level (tube feeding, dysphagia diet, and general diet). The correlation between dysphagia and pulmonary function was analyzed using an independent t-test test with the optimal points, and the relationship between the diet level and pulmonary function was evaluated using a one-way analysis of the variance. Results: Significant correlations between the pulmonary function and sub-items of VDS were found in “oral transit time” with VC, “vallecullar residue” and “aspiration” with PCF, and “triggering of pharyngeal swallow”, “VDS total score” with VC and PCF. The dietary levels upon admission had a significant correlation with VC and PCF. The VC among groups divided according to three diet levels showed statistically significant differences. Conclusion This study revealed the relationship between the pulmonary function and dysphagia in post-stroke patients. Moreover, the pulmonary function correlated with dietary level, even though it was not confirmed that it affected dietary levels. The clinical importance of the pulmonary function in post-stroke patients with dysphagia should be emphasized. In addition, a large-scale study is needed to determine the correlation between the pulmonary function and swallowing difficulty